Bleaching process by means of chlorites



Patented Aug. 18, 1959 ice 2,900,219 BLEACHING PROCESS BY MEANS OF CHLORITES Wilhelm Waibel, Frankfurt am Main, Germany, assignor to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Briining, Frankfurt am Main, Germany, a corporation of Germany No Drawing. Application September 7, 1955 Serial No. 533,005

Claims priority, application Germany September 9, 1954 Claims. (Cl. 8-108) The chlorites, because of their energetic but fiber preserving bleaching eifect are increasingly used for, bleaching cel lulosic as well as entirely synthetic fibers. The materials to be bleached are generally treated at 60 100 C. in aqueous chlorite solutions. Another manner of operating consists in impregnating the material to be treated with chlorite solutions .and subsequently activating the chlorite incorporated in the goods, by means of a steam treatment, at temperatures of slightly more or less than 100 C.

In contradistinction to the bleaching in aqueous solutions the last mentioned process, in addition to a reduced bleaching period, primarily offers the advantage of a more uniform bleaching and an energetic decomposing effect on accompanying substances such as seed husks, flax straw, albuminous substances etc. The disadvantage connected with this process, however, consists in an increase of consumption of the bleaching agents, amounting to 3060%. This higher consumption of bleaching agents is caused partly by the disproportionation of the chlorite to non-bleaching chloride and chlorate, in part by the escaping of chlorine dioxide which is formed to a considerable extent under the conditions of the steaming process. As this gas, besides badly affecting the health, exerts a corrosive action on building structures, and, when discharged into the air, detrimentally influences vegetation, special exhausting devices and absorption plants are required. All these measures render the process more expensiv As regards the exhausting devices and absorption plants, the choice of the construction materials offers difiiculties.

The Belgian Patent 527,711 discloses a process in which the textile material is impregnated with an aqueous chlorite solution and subsequently heated, by means of steam, to temperatures up to 100 C.; then the heated goods are allowed to rest for 1-2V2 hours at the elevated temperature, the time of rest being correlated to the impregnation period. It must amount to 5-15 times the impregnation period. Therefore, a time of rest of 1-2 /2 hours corresponds to an impregnation time of 4-30 minutes. In order to obtain useful results within the aforementioned periods, it is necessary to apply temperatures above 85 C. Thereby, the above-mentioned disadvantages entailed by the steam treatment at about 100 C., i.e. the evolution of large quantities of chlorine dioxide cannot be avoided.

The present invention is based on the observation that it is possible to make use of the advantages of a uniform bleaching and an energetic decomposition effect on the accompanying substances, practically without entailing the above mentioned disadvantages, by impregnating the goods to be treated with a chlorite solution which, thereafter, is caused to act upon the goods at considerably reduced temperatures, preferably between about 40 and about 70 C.

If the goods to be treated are dry, can be carried out on a padding machine;

the impregnation wet goods are advantageously first squeezed or exhausted in order to reduce the moisture content to a value below 100%, and then impregnated by repeatedly dipping them into the impregnation bath and eventually slightly squeezing them. The dipping times usually required amount to less than 60 seconds, in most cases to a range between 2 and 30 seconds.

The impregnation times required for the present procedure are considerably reduced in comparison with the known process. As the goods are heated to and stored at only moderately elevated temperatures no chlorine dioxide is developed. The disadvantages connected with the known process are not entailed by this method of operation and a disproportionation of the chlorite to nonbleaching chloride and chlorate practically does not take place. This means a considerably lower consumption of chlorite and, in consequence thereof, reduced expenses for bleaching agents, while attaining the same bleaching results.

The following examples serve to illustrate the invention but they are not intended to limit it thereto:

EXAMPLE 1 (a) 100 grams of macco (Egyptian cotton) poplin are impregnated at 60 C. with a solution containing:

19 grams per liter of sodium chlorite (of strength) +3 grams per liter of an alkylaryl sulfonate +1.5 grams per liter of methyl taurine and showing a pH value of 4.8. Then the goods are squeezed in order to reach a moisture content of and allowed to rest for 5 hours at the impregnation temperature. Subsequently the goods are washed hot and cold.

(b) 100 grams of macco poplin are impregnated at 40 C. with a solution containing:

31 grams per liter of sodium chlorite (of 80% strength) +3 grams per liter of an alkylaryl sulfonate +1.5 grams per liter of methyl taurine and showing a pH value of 8. Then the goods are squeezed in order to reach a moisture content of 80%. Subsequently, the goods thus treated are exposed for 4 minutes at about 103 C. to an evaporated mixture of water, and formic acid, and then washed hot and cold.

(0) 100 grams of macco poplin are impregnated at 40 C. with a solution containing:

19 grams per liter of sodium chlorite (of 80% strength) +3 grams per liter of an alkylaryl sulfonate +1.5 grams per liter of methyl taurine and showing a pH-value of 3.9. Then the goods are squeezed in order to reach a moisture content of Subsequently, the goods thus treated are heated, for a short time, up to 95 C. by means of steam and allowed to rest for 1 /2 hours at the same temperature. Then the goods are washed as indicated under 1(a).

chlorite (of 80% strength), percent It results from the above figures that when carrying out the process accordingto the present invention, a full white is obtained in an economical manner. Without subjecting the goods to any alkaline treatment, they show 100 grams of a cotton fabric containing a large percentage of husks is impregnated at30 C. with a solution containing 18 grams per liter of sodium chlorite (of +4 grams. per liter of an alkylarylsulfonate and showing a pH value of 4.4. Then the goods are squeezed in order to obtain a moisture content of 100% and allowed to rest for 4 hours at 60 C. The fabric is subsequently treated at 80 C. for 5 minutes with 0.5 gram per liter of a solution of olcylmethyl taurine and then rinsed cold.

80% strength) Supplementary treatment with washing agent Without With Percentage of white 81. i 83. 4

When cotton is to be treated, a preliminary alkaline treatment can of course also be applied whereby the consumption of chlorite is reduced to the same extent as accompanying substances are removed. However, each alkaline treatment usually entails an high loss of weight, a harsh handle, and as the saving in chlorite is compensated by the costs of preliminary treatment, the latter can normally be dispensed with. In contradistinc'tion thereto, the mercerization is of great importance for quite a number of textiles.

EXAMPLE 3 100 grams of a mercerized cotton fabric is impregnated at 25 C. with a solution containing 12.5 grams per liter of sodium chlorite of 80% strength +5 grams per liter of a condensation product of a fatty acid and of clearage products of proteins and showing a pH value of 8;

Then the goods are squeezed in order to obtain according to the invention The process can be applied in the same favorable manner for the bleaching of bast fibers such as linen, hemp, ramie and the like. According to the processes hitherto known it is very difficult to bleach in particular bast fiber fabrics in a uniform manner because of their high content of accompanying substances (for instance pectin, proteins, lignin). In order to remove, from the beginning, a large portion of these accompanying substances a number of boiling operations is required before proceeding to the bleaching itself. Even in these cases, several bleaching operations are required in order to obtain a good white. When applying the process accordingto the invention, the preliminary alkaline treatment can completely or partially be dispensed with; nevertheless, a good and uniform white is obtained.

EXAMPLE 4 l kilo'of alinen fabric of tow yarns containing flax straw is impregnated at 30 C., with a solutioncontainmg 30 grams per liter of sodium chlorite of 80% Strength and showing a pH-value of 4.8. Then the goods are squeezed in order to obtain a moisture content of 100%, and allowed to remain over night at 40 C. Then the goods are treated for 30 minutes at 60 C. by means of water, and rinsed. Then follows a 2 hours after-treatment at -8-0 C. with a solution containing:

0.36 gram per liter of active oxygen 0.25 gram per liter of sodium hydroxide 2.0 grams per liter of calcined sodium carbonate 3.0 grams per liter of water glass of 40 B.

Finally, the goods are rinsed hot and cold. A uniform white of 69.4% white) is obtained. The flax straw is completely removed. The loss in weight amounts to 8.9% only.

The process according to the invention is also appropriate for the bleaching of textile fibers or articles of regenerated cellulose, of cellulose esters and of condensation and polymerisation products inclusive of mixed-condensates and copolymers.

EXAMPLE 5 100 grams of viscose rayon fabrics which are bleached only with difficulty are impregnated at 30 C. with a solu tion containing:

2 grams per liter of sodium chlorite of strength, +3 grams per liter of an alkylphenylpolyglycol ether EXAMPLE 6 100 grams of polyamide fibers are impregnated at 45 C. with a solution containing:

5 grams per liter of sodium chlorite of 80% strength, +3 grams per liter of an alkylarylp'olyglycol ether and showing a pH-value of 4. Then the goods are squeezed in order to obtain a moisture content of 60% and allowed to rest for 2 /2 hours at 65 C. Then they are washed as described above.

EXAMPLE 7 100 grams of a cotton fabric containing a large percentage of husks is at first desized in the usual manner and, after washing, the goods are squeezed or filtered with suction in order to obtain a moisture content of 50%.

Then the moist goods are impregnated with a solution of 25 C. containing 30 grams per liter of sodium chlorite of 80% strength ands'howing a pH value of 4.2. Then they are squeezed in order to obtain a moisture content of 100%. Then the goods are heated to 73 C. by means of superheated steam, rolled up and allowed to rest at this temperature for 3 /2 hours. Subsequently they are washed at first at C. with add'itionof 0.5 gram/ liter of an alkylaryl sulfonate and 0.3 gram/ liter of an alkylphenylpolyglycol ether and then rinsed warm and cold.

I claim:

1. In the impregnating process for the bleaching of textile fibers andfabrics wherein the goods to be bleached are impregnated with an aqueous chlorite solution, squeezed out to about twice the dry weight, and thereafter heat treated at an elevated temperature, the improvement which comprises maintaining the pH of the solution in the squeezed out goods in the range of 3.5 to range of 3.5 to 5, and maintaining the impregnated mate- 5, and effecting the heat treatment by maintaining said rial for about 4 to 5 hours at a temperature ranging goods at a temperature of from about 40 C. to about between about 40 C. to about 70 C. 70 C. for at least about two hours whereby foreign residues in the goods are decomposed while evolution of 5 References Cited ill the file Of is pa e gaseous chlorine dioxide is substantially eliminated. UNITED STATES PATENTS 2. A process as claimed in claim 1, wherein the goods to be treated are first impregnated with a neutral to EZ P; 2 32 weakly alkaline chlorite solution and the chlorite solu- 2521340 C yo 1950 tion incorporated in the goods is brought to a pH value of 10 an 6p 3.5-5 only afterwards by causing a volatile acid and FOREIGN PATENTS steam to act P 527,711 Belgium Apr. 15, 1954 3. A process as claimed in claim 1, whereln acid 52567 Great Britain AIM-14,1943 and chlorite resistant wetting and washing agents are 552,711 Great Britain Apr. 21, 1943 added to the chlorite solutions. 15 7 5 Great Britain 9, 1955 4. A process as clalmed 1n claim 1, wherein the OTHER REFERENCES bleached goods are after-treated by means of a solution containing washing agents. Taylor et al.: Ind. and Eng. Chem, vol. 32, No, 5,

5. The process which comprises impregnating textile-- "July 1940, pp. 899-903. fibrous material with an aqueous l r l qrite sollition, 20 Fenrich et al.: Am. Dyestutf Reporter, May 25, 1942,

squeezing the material to abo 'Sf e g pp. P263-P265. maintaining the H sdi'iftl n in the material in the The Textile Manufacturer, March 1945, pp. 122-123.

UNITED STATES PA IENT QF FICE 7 CERTIFICATE OF CORRECTION Patent No; 2,900,219 August 18, 1959 Wilhelm Waibel It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below In the heading to the printed specification, line 9 thereof, for "Claims priority, application Germany September 9, 1954" read Claims priority, application Germany September 11, 1954 Signed and sealed this 8th day of March 1960.

I (SEAL) Attest:

KARL HQ AXLI-NE v v ROBERT C. WATSON Attesting- Officer Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 Patent No. 2,900,219 I August 18, 1959 Wilhelm Waibel It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected beloWs In the heading to the printed specification, line 9 thereof, for "Claims priority, application Germany September 9, 1954 read Claims priority, application Germany September 11, 1954 Signed and sealed this 8th day of March 1960.

:(SEAL) Attest:

ABL H. AXLINE a ROBE-HT" C. WATSON Attestlng Officer Comissicner of Patents 

